Axial piston machine and control plate for an axial piston machine

ABSTRACT

In the case of a control plate for an axial piston machine having at least two control openings ( 31, 32 ), by means of which cylinder bores ( 9 ) of a cylinder drum ( 4 ) rotatably mounted in a housing ( 2 ) are alternately connected, on rotation of the cylinder drum ( 4 ), to a high-pressure connection and a low-pressure connection, an outwardly extending extension surface ( 40 ) is formed on a partial region of the outer circumference of the control plate ( 20 ), the extension surface being designed for defined bearing against a holding element ( 52, 53 ) of the axial piston machine ( 1 ) in order to achieve a rotation locking for the control plate ( 20 ).

The present invention relates to an axial piston machine and to a control plate for such an axial piston machine.

In axial piston machines, pistons which are arranged longitudinally displaceably in cylinder bores of a cylinder drum perform a stroke movement on each revolution of the cylinder drum, which movement consists of a suction stroke and a pressure stroke. In order to ensure a rotationally synchronous connection between the cylinder drum and the corresponding working line of the axial piston machine, a so-called control plate is situated at the end side of the cylinder drum, in which control plate there are generally formed kidney-shaped control openings for connecting the cylinder drum to a high-pressure connection and a low-pressure connection of the axial piston machine.

A conventional control plate, as is known from the prior art and described, by way of example in a similar form, in DE 102 51 552 B3, is illustrated in FIGS. 5 to 7. The control plate 100 has an outside diameter which corresponds to the inside diameter of a corresponding housing component of the axial piston machine. In the direction of the side facing away from the cylinder drum, the control plate 100 is supported on a housing cover, in which the high-pressure connection and the low-pressure connection of the axial piston machine are formed. The control plate 100 has a plurality of control openings 101 and 102 distributed over its circumference, which are provided for connecting the cylinder drum to the low-pressure connection and to the high-pressure connection, respectively. Besides these control openings 101, 102, the so-called kidney suction opening and the so-called kidney pressure openings, the control plate 100 furthermore has a central cutout which is penetrated by a shaft of the axial piston machine connected to the cylinder drum in a manner fixed against relative rotation. Adjoining this central cutout are two lateral indentations 103 which form a passage for leakage oil. Furthermore, in the edge region there is formed a groove 104, as can be seen in particular from the illustration in FIG. 7, which enables a rotation-locked positioning of the control plate 100. According to the illustration in FIG. 6, this groove 104 cooperates with a pin 110 mounted in the housing of the machine, ensuring that, on the one hand, the plate 100 cannot be fitted in the axial piston machine in a manner rotated by 180° and, on the other hand, no rotation of the plate 100 occurs during operation either.

Such control plates have proved their worth many time in the past, but require a relatively complex working process for their production. In this process, the plates are usually produced from slugs or rough stampings or forgings by machining, the appropriate parts being completely machined on all surfaces. In this working process, in particular the kidney suction opening 101, the kidney pressure openings, the leakage oil passages 103 and the groove 104 for the rotation locking are cut out.

The object on which the present invention is now based is to specify a novel distributing or control plate for an axial piston machine which, on the one hand, is at least equivalent to the known control plates as regards its operating properties, but, on the other hand, can be produced more simply and cost-effectively.

The object is achieved according to the invention by a control plate for an axial piston machine having the features of claim 1 and an axial piston machine having the features of claim 11. Advantageous developments of the invention are the subject-matter of the dependent claims.

The solution according to the invention is based on the idea of configuring the control plate in such a way that an outwardly extending extension surface is formed on a partial region of the outer circumference of the control plate, the extension surface being designed in such a way that it enables a defined bearing against a holding element of the axial piston machine in order to achieve a rotation locking for the control plate. For this purpose, the extension surface may, for example, have a straight edge region which is suitable for bearing against a plane wall of a corresponding holding element. Furthermore, an edge recess in the extension surface would also be conceivable or a protuberance, which can cooperate, for example, with an oval or cylindrically configured holding element or with a corresponding recess in the holding element, respectively.

According to the invention, a control plate for an axial piston machine having at least two control openings, by means of which cylinder bores of a cylinder drum rotatably mounted in a housing are alternately connected, on rotation of the cylinder drum, to a high-pressure connection and a low-pressure connection, is accordingly specified, it being provided according to the invention that an outwardly extending extension surface is formed on a partial region of the outer circumference of the control plate, the extension surface being designed for defined bearing against a holding element of the axial piston machine in order to achieve a rotation locking for the control plate.

The advantage of the solution according to the invention is that the known pin-and-groove connection for achieving the rotation locking can be dispensed with. In contrast to the groove illustrated in FIGS. 5 and 7, in the control plate according to the invention the rotation locking is achieved by a special shaping of the outer circumference or outer contour of the control plate, which affords the advantage that the edge recesses provided, for example, for this can be designed to be continuous, i.e. over the entire thickness of the control plate. This, in turn, means that it is possible to produce the control plate according to the invention in a simple manner by a stamping process, during which the outer contour, the inner contour and the kidney regions of the control plate can be created directly. All that is then still required is a finishing of the two plane bearing surfaces of the control plate, which affords significant advantages in the production. As an alternative to this, the control plate could also be produced by laser cutting, in which case a finishing of the plane surfaces is then unnecessary, since a high-quality input stock with the required surface finish can be used. Both methods can be used only to a limited extent for the control plate according to the prior art, since the formation of the groove for the rotation locking can only be produced by machining the plate.

Developments of the concept according to the invention relate, in particular, to measures which can additionally reduce the material expenditure for and the space requirement of the control plate. In this regard, it may be provided, for example, that the outer edge region of the control plate is reduced in the radial direction in the region of the at least one control opening connected to the low-pressure connection. Furthermore, the radially inner edge of the control plate may be designed as a centring surface which centres the control plate on a centring body on the housing. This centring surface may be composed of a plurality of partial surfaces formed on segments of the inner edge of the control plate which extend radially inwardly into the through-opening. The radial extent of the individual recesses is, in this case, preferably of such a size that a gap results in the region of the recesses between the control plate and the centring body, which gap is suitable for allowing a leakage fluid which has accumulated in the interior of the cylinder drum to pass through.

According to the invention, an axial piston machine having a cylinder drum which is rotatably mounted in a housing and in which are made cylinder bores, in which pistons are axially displaceably arranged, the cylinder bores having openings towards an end side of the cylinder drum, which are alternately in connection, on a rotation of the cylinder drum, with a high-pressure connection and low-pressure connection via at least two control openings of a control plate, is furthermore proposed, the control plate being designed according to the above-described concept according to the invention. Advantageously, the machine is designed as a swash-plate machine, it then being possible for the holding element for the rotation-locked positioning of the control plate to be formed by the setting piston guide.

The invention will be explained in more detail below with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic illustration of an axial piston machine configured according to the invention;

FIG. 2 shows an illustration of a first exemplary embodiment of a control plate according to the invention;

FIG. 3 shows the arrangement of the control plate according to the invention of FIG. 2 in the axial piston machine;

FIG. 4 shows the arrangement of an alternative embodiment of a control plate according to the invention in an axial piston machine, and

FIGS. 5 to 7 show the configuration and arrangement of a control plate of an axial piston machine according to the prior art.

The axial piston machine according to the invention which is illustrated in FIG. 1 and provided generally with the reference symbol 1 is configured largely identically to the axial piston machine known from DE 102 51 552 B3. The construction and function of the known components of the machine 1 will therefore be merely briefly summarised in the following.

The axial piston machine 1 has a shaft 3 which is rotatably mounted in a housing 2 and on which a cylinder drum 4 is arranged, the cylinder drum 4 and the shaft 3 being connected to one another in a manner fixed against relative rotation. The shaft 3 penetrates the cylinder drum 4 and is mounted on both sides of the cylinder drum 4 with the aid of a rolling bearing 5 and 6, respectively, the lower rolling bearing 6 having in particular an outer bearing race 7 which is inserted into a corresponding recess of a housing cover 8 of the axial piston machine 1.

A plurality of cylinder bores 9 are formed in the cylinder drum 4 in a manner distributed over the circumference, the centre axes of the cylinder bores 9 running parallel or obliquely to the centre axis of the shaft 3. Inserted axially displaceably in these bores 9 are pistons 10 having, on the side facing away from the housing cover 8, a spherical head 11 which cooperates with a corresponding recess of a slide shoe 12 to form a knuckle joint. The piston 10 is supported on a swash plate 13 by means of the slide shoe 12, so that on one revolution of the cylinder drum 4, the pistons 10 accordingly perform an alternating stroke movement. The length of stroke is predetermined here by the position of the swash plate 13, which can be adjusted about a tilting axis running perpendicularly to the longitudinal axis of the shaft 3. For this purpose, there is provided an adjusting device 14 with a piston 50 which cooperates at its two ends with the swash plate 13 on the one hand and with a setting piston guide 51 on the other hand. The configuration in particular of this cylinder-like or pot-like setting piston guide 51 will be explained in more detail at a later time.

The cylinder drum 4 has a central opening 15, in which there is arranged a compression spring 16 which is clamped between a first spring bearing 17 and a second spring bearing 18. The first spring bearing 17 is fixed here in the axial direction on the shaft 3, whereas the second spring bearing 18, in contrast, is formed by a Seeger circlip ring inserted into a groove of the cylinder drum 4. Through the force of the compression spring 16, the cylinder drum 4 is displaced in the axial direction to such an extent that its end face 19 bears sealingly on the control plate 20.

The control openings, not evident in the sectional illustration according to FIG. 1, of the control plate 20 are, on each side facing away from the cylinder drum, in permanent contact with at least one high-pressure connection and one low-pressure connection of the axial piston machine 1. The cylinder bores 9 of the drum 4 are open towards the end face 19 of the cylinder drum 4 via corresponding openings 21, these openings 21, on rotation of the drum 4, passing over the control plate and thereby being alternately connected to the control openings for the high-pressure connection and the low-pressure connection, respectively.

The position of the control plate 20 is fixed with respect to the shaft 3 firstly by a centring surface 29, the configuration of which will be explained in more detail below. A through-opening of the control plate 20 has, for this purpose, a radial extent corresponding to the outer radial extent of a centring body which is connected to a housing component. In the exemplary embodiment illustrated, the centring body is formed by the outer bearing race 7 of the rolling bearing 6. In the axial direction, the control plate 20 is supported on the housing cover 8, and, to avoid leakage, the control plate 20 has a sealing surrounding area 28 which is formed on the side of the control plate 20 facing away from the cylinder drum 4 and cooperates sealingly with the surface of the housing cover 8.

For a correct operation of the axial piston machine 1, besides a centred arrangement of the control plate 20 an appropriate orientation is also required, it being necessary to ensure that no rotation of the control plate 20 takes place during the operation of the machine 1 either. While the pin-and-groove connection described in the introduction is used for this purpose in the prior art, according to the invention it is now proposed to configure the control plate 20 in a special way, so that a rotation-locked arrangement is again achieved, but the pin-and-groove connection can be dispensed with and accordingly the production of the control plate 20 can be simplified. A first exemplary embodiment of an appropriately configured control plate will now be explained with reference to FIGS. 2 and 3.

First of all, in FIG. 2 the control plate 20 with the central opening 30 and the control opening 31 for the low-pressure connection and three control openings 32 for the high-pressure connection can be seen. The central through-opening 30 has in this case a diameter corresponding to the outer circumference of the bearing race 7 of the rolling bearing 6. The inner edge 33 of the through-opening 30 accordingly forms the above-mentioned centring surface 29. The through-opening 30 is furthermore widened by two recesses 34 and 35, between each of which segments are formed, so that the centring surface 29 is ultimately formed by the partial surface 29.1 and 29.2 on the segments. As a result of the recesses 34 and 35, a gap 22 (see FIG. 1) is formed partially at the circumference of the outer bearing race 7, through which gap a leakage fluid can pass.

The special feature, according to the invention, of the control plate 20 consists in an outwardly extending extension surface 40 in the upper region of the outer circumference. This extension surface 40 is configured in a special way in its edge region 41, in order to enable a defined bearing relative to a holding element of the axial piston machine. This enables a rotation-locked arrangement of the control plate 20, despite dispensing with the pin-and-groove connection.

In the exemplary embodiment of FIGS. 2 and 3, the extension surface 40 has a straight edge region 41, which can accordingly cooperate with a plane wall of a holding element. According to the illustration in FIG. 3, provision is preferably made, for this purpose, for the setting piston guide 51 already mentioned above to be used as the holding element. This setting piston guide has a cylinder 52, the lower end of which rests on a disc 53. This disc 53 is in this case likewise cut off straight in its edge region 54, so that the edge region 41 of the extension 40 of the control plate 20 can bear in a plane manner against the edge region of the disc 54, as illustrated in FIG. 3. This prevents in an effective way a rotation of the control plate 20 during the operation of the axial piston machine 1.

The advantage of the configuration, according to the invention, of the control plate 20 is that the corresponding configuration of the edge region 41 of the extension 40 can extend over the entire height or thickness of the control plate 20. This enables production of the control plate 20 in a relatively simple and cost-effective manner. For example, a simple stamping-out of the control plate 20 would be conceivable, during which the outer contour, the inner contour and the kidney regions could be created at the same time. In this case, all that would still be required is a finishing on the two plane bearing surfaces of the control plate 20. As an alternative to this, however, an appropriately shaped blank could also be machined by laser cutting, in which case a finishing of the plane surfaces is then no longer required, since a high-quality input stock with the necessary surface finish can already be used. Both variants are significantly simpler to carry out than the machining of slugs or rough stampings or forgings which has been required hitherto for the production of control plates. At the same time, however, the functionality of the control plate is fully preserved, since the appropriate configuration of the edge region 41 of the extension 40 means that the desired rotation locking is achieved as before.

Further measures concerning the shaping of the control plate 20 which additionally optimise the material expenditure and the space requirement can be gathered from FIGS. 2 and 3. Thus, on the one hand, provision may be made for the outer region 42 of the control plate to be reduced in the radial direction in the region of the low-pressure control opening 31. As a result, on the one hand the space requirement and on the other hand the material expenditure is thus reduced. Furthermore, openings are formed by appropriate indentations 43 and 44 in the edge region 41 of the extension surface and/or in an edge region of the control plate 20 opposite the extension surface 40, which openings serve to carry off the pumping leakage oil without loss.

FIG. 4 shows an alternative embodiment of a control plate 20 according to the invention which differs in the configuration of the edge region of the extension surface 40. In this case, the control piston guide 51 is designed merely as an upwardly extending cylinder 52, the edge region 41 of the extension surface 40 then having an edge recess 45 which cooperates with the cylindrical outer contour of the cylinder 52. Again, a rotation of the control plate 20 during the operation of the axial piston machine is precluded by this configuration. Furthermore, it would be conceivable to configure the extension surface, in the edge region, with a protuberance or projection which then cooperates with a corresponding depression or recess in the holding element.

Overall, therefore, the present invention opens up the possibility of simpler and more cost-effective production of control plates for axial piston machines. At the same time, however, an exact arrangement and orientation of the control plate in the axial piston machine is ensured as before. 

1. Control plate for an axial piston machine having at least two control openings, by means of which cylinder bores of a cylinder drum rotatably mounted in a housing are alternately connected, on rotation of the cylinder drum, to a high-pressure connection and a low-pressure connection, wherein an outwardly extending extension surface is formed on a partial region of the outer circumference of the control plate, the extension surface being designed for defined bearing against a holding element of the axial piston machine in order to achieve a rotation locking for the control plate.
 2. Control plate according to claim 1, wherein the extension surface has a straight edge region for bearing against a plane wall of the holding element.
 3. Control plate according to claim 2, wherein the extension surface has an edge recess.
 4. Control plate according to claim 3, wherein the recess is designed to cooperate with an oval or cylindrical holding element.
 5. Control plate according to claim 1, wherein an indentation is formed in the edge region of the extension surface and/or in an edge region of the control plate opposite the extension surface.
 6. Control plate according to claim 1, wherein a through-opening is formed in the control plate, the radially inner edge of the control plate being designed as a centring surface which centres the control plate on a centring body on the housing.
 7. Control plate according to claim 6, wherein the centring surface is composed of a plurality of partial surfaces formed on segments of the inner edge of the control plate which extend radially inwardly into the through-opening and are separated from one another by recesses.
 8. Control plate according to claim 7, wherein the radial extent of the individual recesses is of such a size that a gap results in the region of the recesses between the control plate and the centring body.
 9. Control plate according to claim 1, wherein the outer edge region of the control plate is reduced in the radial direction in the region of the at least one control opening connected to the low-pressure connection.
 10. Control plate according to claim 1, wherein it is formed by a stamping.
 11. Axial piston machine having a cylinder drum which is rotatably mounted in a housing and in which are made cylinder bores, in which pistons are axially displaceably arranged, the cylinder bores having openings towards an end side of the cylinder drum, which are alternately in connection, on a rotation of the cylinder drum, with a high-pressure connection and low-pressure connection via at least two control openings of a control plate, wherein the control plate is designed according to claim
 1. 12. Control plate according to claim 11, wherein the machine is designed as a swash-plate machine, the holding element being formed by a setting piston guide.
 13. Axial piston machine according to claim 11, wherein a through-opening is formed in the control plate, and in that the cylinder drum is arranged on a shaft in a manner fixed against relative rotation, the shaft being mounted in the housing on the side of the control plate, and the control plate being centred on an outer bearing race of a rolling bearing by a centring surface formed on the inner edge of the control plate. 